I eat a little bit of everything I want, but not a lot of anything. If I overdo it one day, I won't indulge the next.

Is it true you cooked lunch for Prince William and Duchess Catherine in 2011?

Yes, I did. Prince William told me he'd been trying to perfect lasagna for years. He wanted to impress the Duchess; her family makes good lasagna, and his could never stand up to it. I tried to give him tips—but I just couldn't believe I was talking to him.

What's your biggest advice for a new cook?

Build a repertoire with a handful of recipes you've practiced and can make well. Then explore new things.

Let's talk easy weekday foods. Got a tip for making a better sandwich?

Instead of mayo, smear pesto—store-bought or homemade—on bread. It's better than any other spread.